Pyrometer tube



Aug. 26, 1930. F. c. SIMMS PYROMETER TUBE Filed Nov. 4, 1927 I I I I I 1 /I/ l'/ I INVENTOR Frank C.6imms.

ATTORNEY Patented Aug 26, 1930 .UEETED ST FRANK o. snvnvrs-or EAST PALESTINE, OHIO PYRoME'rEit TUBE Application filed November 4, 1927'. Serial No. 230,994.

My invention relates totemperature meas-' uring devices and particularly to pyrometer tube a An object of my invention is to provide a structure for a pyrometer tube that shall permit of the tube being quickly inserted in and withdrawn from the chamber of a furnace without danger of cracking or breaking.

Another object. of my invention is to provide a unitary pyrometer tube that shall embody a gas tight inner refractory portion'and av heat-insulating or heat-equalizing outer ceramic portion.

In practicing my invention I provide an inner tube-Which is composed either of a highly refractory metal or of porcelain which has been made and fired: in the usual manner, the inner tube being surrounded or covered by a relatively thick coating of a highly refractory cement consisting of a high temperature clay and fused alumina.

In the single sheet of drawings,

v Figure l is a view, in longitudinal section, of a device embodying my invention, and,

Fig. 2 is a view, in vertical lateral section, of a furnace with which is associated the device embodying my invention.

It has heretofore been found necessary to use a substantially stationary tube supported by and in one of the walls of a furnace and extending therethrough into the furnace chamber, this tube being of ordinary refractory material and of such diameter as to permit of fitting thereinto a smaller ceramic tube within Which is located the usual thermocouple, by means of Which, when used in combination with suitable indicating instruments the temperature of the furnace chamber may be measured. It has been found necessary to insert and withdraw the inner tube very slowly in order to avoid breaking it because of the change in temperature to which it is subjected.

Referring more particularly to Fig. 1 of the drawing I have there illustrated a pyrometer tube assembly 11 embodying an inner tube 12 which is made either of a highly refractory metal such as nickel, or of porcelain which has been fired at a suitable temperature of about 2000 F. I provide an outer cement coating or tube 13 therearound, com prising a mixture of comminuted fused alumina, a high temperature clay, and a small amount of a suitable binder such as dextrine. I prefer touse amixture of approximately 30% of high tempera'ture'clay and approximately of fused alumina, although I de sire it to be understood'that this proportion may be departed from to a certain extent. Enough binder is added to the finely divided mixed dry clay and fused alumina: to make a relatively moist mixture of the general consistency of heavy cream. i i I The tube 12 isjthen dipped into this moistened cement mixture a sufficient number of times to provide a relatively heavy closely adherent coating around the exterior of the porcelain tube. It may be necessary to permit each coating to dry for a short period of time in air beforeanother dipping in order that. it may be possible to provide a coating that shall be of even thickness over v the entire area thereof.

As shown in the drawing oneend of the tube is closed. While I have indicated that the wall-thickness of the inner tube is slightly less than that of the outer tube, I do not desire to be limited thereto as the relative thicknesses of the wall are of no particular moment, except that boththicknesses should be relatively large and I prefer that the radial thickness of the outertube shall be not less than inch, and I may make it two or three times this value.

After the plurality of coatings have been permitted to dry in air I place the tube in a suitable furnace chamberoperatingat a temperature of not lessthan 2000?, and possibly up to 3000 F. The firing is continued until the inner tubel2has been refused to a greatv or extent than occurred during its initial firing, if made of porcelain, theeifect being that the inner tubeiis rendered substantially gastight. This is .of importance in the case of certain furnace. operations in which there might be a tendency for the atmosphere in the chamber to be,of an oxidizing character and to penetrate the walls of the tube. r

If theinner tube is of a highly. refractory metal, such as nickel, the firing temperature must be such that the nickel or other metal is not softened or otherwise affected in a manner to reduce the cementing action of the mixture of fused alumina and high tem- K perature clay. It may be noted here that the term high temperature clay is a generic one and is here used to cover any clay that will withstand relatively high temperatures, irrespective of the composition thereof. This coating or outer tube Will adhere closely to the inner tube being cemented thereto by its own adhesive action and will withstand or resist the action of slag, acid, or'oxie dizing atmosphere. It is made thick enough to have a heat-equalizing effect an-d'is thus able to withstand sudden relatively great changes in temperature without cracking or breakin Fig. A illustrates theuse of the pyrometer tube embodying my invention. A. furnace is indicated generally by 1aand comprises a plurality of Walls of heat-insulating and high temperature resisting bricks or blocks surrounding a furnace chamber 15. An opcning 16 is provided in one of the walls of the furnace of such size as to receive the pyrometer tube' 11. A thermocouple 17 is located within the inner tube 12, the joint thereof being located within the furnace chamber to 15, the tube 11 extending sufficiently far into the furnace chamber to subject the thermocouple joint to the operating temperature of the chamber. The two wires of'the thermocouple are connected to a suitable temperature indicating means usually employed in the art, by means of which the operating temperature of the furnace chamber may be dete mined.

I have found, by actual tests, that it ispossible to quickly insert a composite pyrometer tube of the kind embodying my invention through the opening 16 in a furnace Wall, without the tube cracking or breakin l iave found it possible also to quickly remove such a pyrometer tube from the furnace structure without its cracking or breaking, even though the temperature of the furnace be well'above 2000 F. I attribute this to the relatively thick protective and heat-equalizing coating on the outside of the inner refractory tube, which protective coating or tubing is made of such thickness and of such material as to permit of its being'subjected to relatively rapid and large temperature changes without overstressing the walls of the tube. Various modifications may be made in the device embodying my invention without departing from the spirit and scope thereof,and I desire therefore, that only such limitations shall be placed thereron as are imposed by the prior art or are set forth in the appended claims.

I claim as invention:

composite pyrometer tube structure comprising an inner tube of refractory material and an outer heat-equalizing tube of refractory ceramic material therearound and intimately bonded thereto by firing,

2. As a new article of manufacture, a fire-d composite unitary pyrometer tube structure comprising an inner tube of refractory material and an outer closely adherent coating of a hi hly refractory material comprising fused alumina, clay, and a binder, said coating and tube being intimately bonded by firing the coated tube.

3. As a. new article of manufacture, a fired composite unitary pyrometer tube structure comprising an inner tube of gas proof porcelain, and an outer closely adherent coating, of

' substantially the same or greater thickness as the inner tube, and comprising fused alumina, a high temperature clay and a binder, said coating and tube being intimately bonded by firing the coated tube. I

4:. As a new article of manufacture, a fired composite unitary pyrometer tube comprising a doubly fired inner tube of gas proof porcelain and a singly fired outer closely-adherent heat equalizing covering therearound comprising fused alumina, a high temperature clay and a binder, said covering and tube being intimately bonded by jointly firing the tube and covering.

5. As a new article of manufacture, a fired composite unitary pyrometer tube comprising a doubly fired inner tube of porcelain and a singly fired outer closely-adherentcovering therearound comprising a mixture of approximately fused alumina, and approximately 7 0% of a high temperature clay, said covering and tube being intimately bonded by jointly firing the tube and covering.

In testimony whereof, I have hereunto subscribed my name this 10th day of October, 1927.

FRANK o. siMMs.

1. As a new article of manufacture of the class described, a fired unitaryrefractory 

